Up to now the need and the desire for communication has steadily increased and has now reached an extent such that communication means are ubiquitous in today's life and society. Further, among various communication possibilities, wireless communication has established itself as an option for day-to-day communication needs that is equal to, if not in some cases superior over, wired communication solutions. With wireless communication any distance from several hundreds of kilometers to millimeters can be bridged, depending on the technique and transmitting power used.
In recent years different methods for communication over short ranges, e.g. several centimeters, as well as different methods for communication over ranges up to several meters have been extensively investigated.
For example, a combination of smart cards and radio frequency identification (RFID) tags is widely used in various fields such as transport (ticketing, road tolling, baggage tagging), finance (debit and credit cards, electronic purse, merchant card), communications (SIM card for GSM phone), and tracking (access control, inventory management, asset tracking). In electronic ticketing for public transport, for example, a traveller just waves his/her card over a reader at a turnstile or entry point. The RFID tag of the card is coupled to the reader, and a respective fare is deducted from the card.
Another example of a method for communication over short ranges is body coupled communication (BCC). BCC is a wireless technology that allows electronic devices on and near the human body (up to about 15 cm) to exchange digital information through near-field electrostatic coupling. Information is transmitted by modulating electric fields and electrostatically (capacitively) coupling picoamp currents into the body. The body conducts the tiny currents to body mounted receivers. The environment (the air and earth ground) provides a return path for a transmitted signal.
A further example of a communication method for short ranges is near field communication (NFC), wherein a short-distance communication via networking technology is established between two devices that are not physically connected. Such devices can communicate with each other either peer-to-peer or on a client-server basis. NFC is optimised for easy and secure communications between various devices, e.g. mobile phones, without user configuration. In order to make two devices communicate, users bring them close together or even make them touch. The devices' NFC interfaces will automatically connect and configure themselves to form e.g. a peer-to-peer network. NFC can also bootstrap other protocols like Bluetooth™ or Wireless Ethernet (WiFi) by exchanging the configuration and session data.
However, NFC has two severe limitations. On the one hand, the communication range is limited to about 10-20 cm, which is not always sufficient to perform a desired action. Therefore, it is always necessary to bring a NFC enabled device close to a respective reading terminal. On the other hand, in view of the communication range, financial or other security critical transactions are insecure, as eavesdropping of the communication is possible.